Different Radio Access Technologies (RATs) are available for mobile communications, allowing a user of a user device such as a mobile terminal (termed herein User Equipment, UE) to access communication services like voice calls, Internet browsing, video calls, file transmissions, audio/video streaming, electronic messaging and e-commerce. RATs can be divided into different categories.
A first category includes RATs suitable for use in mobile or cellular telecommunications systems like GSM (Global System for Mobile Communications), UMTS (Universal Mobile Telecommunications System), FOMA (Freedom of Mobile Multimedia Access), EPS (Evolved Packet System), D-AMPS (Digital-Advanced Mobile Phone Service), CDMA2000 (Code Division Multiple Access 2000) or WiMAX (Worldwide Interoperability for Microwave Access). Common examples of RATs in this first category are 3GPP (3rd Generation Partnership Project) GPRS/EDGE (General Packet Radio Service/Enhanced Data rates for Global Evolution), 3GPP WCDMA/HSPA (Wideband Code Division Multiple Access/High-Speed Packet Access), 3GPP LTE/E-UTRAN (Long-Term Evolution/Evolved Universal Terrestrial Radio Access Network), and TD-SCDMA (Time Division Synchronous Code Division Multiple Access).
A second category includes RATs which are suitable for use in short-range wireless communication networks, such as Wi-Fi or WLAN (Wireless Local Area Network). One example of a RAT in this second category is the IEEE 802.11 family of wireless standards. Other examples include Bluetooth and NFC (Near-Field Communication).
Many UEs are enabled for use with more than one RAT, such as one or more RATs selected from the first category, as well as one or more RATs selected from the second category. A UE, enabled both for cellular access (e.g. 3GPP LTE/E-UTRAN and/or WCDMA/HSPA for use in EPS and/or UMTS) and for Wi-Fi access, is used herein as an example of a multi-RAT-enabled user device.
It may be desirable for 3GPP operators to move data traffic from a cellular networks to an alternative access network such as Wi-Fi, in order to reduce the load on the cellular network, and because Wi-Fi access typically uses unlicensed spectrum. However, owing to the inherent differences in architecture and operation between mobile telecommunications networks on the one hand and Wi-Fi networks on the other hand, in many existing setups there has not been any integration between the two. Allowing two such networks to co-exist in parallel but “hidden” from each other is fully acceptable, but not optimal from resource utilization, load distribution and user experience perspectives. Therefore, certain integration attempts have been made, in particular to use Wi-Fi to offload traffic from mobile networks. The existing mobility towards Wi-Fi is controlled by vendor-specific implementations. A common basic principle is for the UE to attempt to access and associate to a known Wi-Fi Access Point (AP) whenever it is detected. However, this does not take into account the load on the cellular network or the Wi-Fi network, which may result in a worse performance for the use.
FIG. 1 illustrates a network architecture for integration of a mobile telecommunications system 1 in the form of an Evolved Packet System (EPS) and a Wi-Fi access network 2. EPS was introduced in 3GPP Release 8 and Release 9. For detailed information about EPS, reference is made to 3GPP TS 23.401. The mobile EPS system 1 comprises an E-UTRAN 3 and an EPC 4. The E-UTRAN 3 has a combined base station and radio network controller known as eNodeB. The EPC 4 has units known as MME (Mobility Management Entity) and a Serving Gateway (SGW). The eNodeB is connected via the S1 interfaces, S1-MME and S1-U to the MME and SGW respectively. FIG. 1 also shows how the Wi-Fi access network 2 is connected to the Packet Data Network (PDN)-GW via the S2a interface and to the 3GPP AAA Server via the STa interface. The shown Wi-Fi access network is an exemplary deployment and contains a Wi-Fi Access Point (AP), a Wi-Fi Access Controller (AC) and a Broadband Network Gateway (BNG). In another example, the Wi-Fi AP may be co-located with a Residential Gateway (RG). In a further example, the Wi-Fi network may also comprise a Trusted WLAN Access Gateway (TWAG). In addition, the interface between the Wi-Fi AC and the PDN GW, i.e. the S2a interface, may also be implemented between the PDN GW and for example either the BNG or the RG.
Wi-Fi integration into Radio Access Network (RAN) may be either by combining both 3GPP and Wi-Fi in small pico base stations to gain access to the Wi-Fi sites with 3GPP technology and vice versa, or by integrating the Wi-Fi access tighter into the RAN by introducing enhanced network controlled traffic steering between 3GPP and Wi-Fi based on knowledge about the total situation on the different accesses. For this second level of integration, issues with UE controlled Wi-Fi selection must be avoided, such as selecting Wi-Fi when the Wi-Fi connection is bad or when the UE is moving, thus giving better end user performance and better utilization of the combined Wi-Fi and cellular radio network resources.
As a UE may access a service network via one or more different RANs, it is possible that a service suitable for one RAN may not be suitable for transmission via another RAN. For example, a Wi-Fi RAN may be much less congested than a 3GPP RAN. There is therefore a requirement for a ‘service aware’ node in the core network domain or in the service layer domain to adjust a level of service provided to the UE depending on the RAN being used or the conditions of the RAN being used. Consider the case where a UE receives streaming video. If a node in the core network domain or in the service layer domain can determine local conditions, it can adjust a quality and/or resolution of the video to ensure that the user experience is not impacted by poor network conditions. However, it is possible that two or more UEs may be allocated the same identifier (such as an IP address) by different gateway nodes or even by the same gateway node if they connect to different PDNs, the PDN to use is indicated by the Access Point Name (APN) and a gateway can support multiple APNs/PDNs. In this case a service aware node is unable to unambiguously identify a UE receiving data that is subject to modification by a service aware node since the only identifier available to a service aware node is the UE IP address.